The present invention relates to a numerical control system for automatically controlling a lathe based on numerical information.
Lathes that are numerically controlled include ordinary lathes and turret lathes. Many such numerically controlled lathes have tool holders for holding cutting tools, the tool holders being disposed in the longitudinal direction of a workpiece, i.e., the Z-axis direction. In those lathes of the type in which the tool holder is turned for changing cutting tools, the tools are attached to the tool holder such that the tip of each of the tools is in the same position with respect to the workpiece when the tool holder is turned for a tool exchange, so that the tools can be changed conveniently. Thus, when the tool used in a preceding process is retracted prior to cutting a workpiece and the tool holder is turned to use a tool in the next process, the values of the position of the tool tip on the X and Z-axes can be used in an NC program as value settings in the coordinate system in the next process.
In the aforesaid procedure, the tool that has been used to cut the workpiece in the preceding process is retracted for a tool exchange, the tool holder is turned to select a tool in the following process, and the selected tool is advanced to a position for cutting the workpiece and moved into contact with the workpiece to cut the workpiece in the next process. Therefore, where different processes are involved, the tool holder is retracted, turned, and advanced each time tools are changed, during that time no cutting operation is effected, resulting in a disadvantage in which the cutting procedure is time-consuming.
The present invention has been made in an effort to solve the aforesaid conventional drawback.